Vapor lock is alive and well in Fl.

[trainguy]

ln the past I have been skeptical about the existence of vapor lock.While in Fl. For the Barners bash in the wonderful 80 deg. Weather the engine stumbled whlIe driving in stop and go traffic and would be difficult to start when hot.It would run flawlessly in the cool mornings a evenings.Vic P assures me that a electric fuel pump will cure the problem.I believe he is correct.

[51 MERC-CT]

And it doesn't have to be a full time electric pump, just a part time pump to be used when the problem arises.

[trainguy]

Originally Posted by 51 MERC-CT

And it doesn't have to be a full time electric pump, just a part time pump to be used when the problem arises.

That is my plan.Im going to use a spring off toggle switch to control the pump.

[Old Henry]

Originally Posted by trainguy

That is my plan.Im going to use a spring off toggle switch to control the pump.

My experience with vapor lock is that it is not always solved by a very brief shot from the electric pump. Often the pump needs to stay on for a while, especially climbing hills and stop and go traffic. I use a regular toggle switch and a very small LED indicator light to remind me that it's on. However, to leave it on probably needs a pressure regulator to limit the pressure.



Here's my pump installation back by the gas tank:



Here's the regulator in the line just after the electric pump:

[oldskool]

airtex as a backup is a good pump to use 6v or 12v models

[green50]

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Originally Posted by trainguy

ln the past I have been skeptical about the existence of vapor lock.While in Fl. For the Barners bash in the wonderful 80 deg. Weather the engine stumbled whlIe driving in stop and go traffic and would be difficult to start when hot.It would run flawlessly in the cool mornings a evenings.Vic P assures me that a electric fuel pump will cure the problem.I believe he is correct.

Just curious, what kind of gas are you running? Ethanol or ethanol-free?

[flatford8]

Hey Phil, remember when we were working on your brakes at VICS I said there was a bracket underneath there to hold an electric fuel pump. Maybe that's been a problem with that car before....... Mark

[trainguy]

Originally Posted by flatford8

Hey Phil, remember when we were working on your brakes at VICS I said there was a bracket underneath there to hold an electric fuel pump. Maybe that's been a problem with that car before....... Mark

I was running the infamous "corn gas".as far as the bracket,I believe at some time it held a electric pump,I'm going to reuse it .I have a low pressure Airtex.Phil

[COE Dan]

I've had vapor lock issues on my '39. In Hawaii, non-ethanol gas was readily available so I switched and that solved the problem. However, since I've moved to Illinois, non-ethanol gas is not available in my area (might have something to do with the cornfield growing behind my house).

One concern I had based upon brief conversations was that an electric in-line fuel pump could damage a weak diaphragm in the mechanical pump. If this happens, fuel will pass through the damaged diaphragm, into the oil filler neck, and ultimately into the crankcase and the oil.

Can anyone verify if this is a valid concern or not?

I'd like to keep my mechanical pump but I don't want the unreliability created by vapor lock but I also don't want to risk premature mechanical pump failure and its associated problems.

COE Dan

[30-9]

Dan

Can but unlikely also that can happen without a electric pump should it go bad

[Roger/Sacramento]

Installing an electric pump in addition to the stock mechanical pump has been discussed in previous postings. Here is my situation. No trouble with vapor lock originally while running only a stock pump. My concern was having to turn over the motor for too long because of dry carburetors. Hard on the starter. I installed an electric pump in the line near the gas tank with a switch on the dash. Pump up the carbs for a few seconds and then turn the switch off. Works great. The problem with my setup is if I am running over 2000 rpm the mechanical is not able to pull enough gas thru the electric pump for proper running. So I have to constantly flip the switch off and on while driving. I don't like leaving the switch on full time because the electric pump pushes gas through the gasket on the mechanical pump and that could be a fire hazard. I do not have a regulator because the electric pump is a 4 lb. unit. I don't have a problem with too much pressure on the carb. needle valves.

[trainguy]

The downside to a electric pumping thru a mech pump is if the diaphram is defective gasoline can get into the crankcase.Therefor I don't run the pump full time I use it just for starting after setting idle for more than a week or to cope with vapor lock.Phil

[AKCJ]

I've read a good argument for running the aux electric pump in parallel with the main fuel line instead of in series. Requires a check valve.

[Lawrie]

In my 33 with the stock babbit engine vapor lock was not a problem.
But with the 99a engine it is,we had a few problems coming back from a trip out west (39 C)and ended up stopped,I wrapped a rag around the fuel pump and poured water on it and away we went.
I have fitted an air scoop in the gap between the radiator and the edge of the grill and a hose goes from this to the fuel pump.
my thoughts are to get some cooler air from in front of the rad and onto the fuel pump.
I haven't been away again yet so don't know the results,but will take the temp gun with me.
Lawrie

[Vic Piano]

I had the '39 CS out today, temps in the mid 80's. I run a 6 volt electric fuel pump, full time, I converted the OEM fuel pump to a pass through. I don't like using an electric pump in line with the OEM pump for the same reason that COE Dan mentioned. The '39 ran well (I also use Skips water pumps, and a modern style coil). On the open road she runs at 180 degrees and in heavy stop and go traffic, she'll creep up to 195+ depending on how long we sit in traffic. I was out taking care of honey-do's and I stopped at the dry cleaners, shut the car off, and went inside for about 3 or 4 minutes. When I got back in the '39, I put the ignition switch on, waited about 10 seconds and hit the starter button... she cranked but did not fire, I'm guessing that the heat had vaporized the fuel in the carb and the line from the fuel pump up to the carb. I didn't want to keep cranking the car so, I removed the air cleaner, hand chocked the carb and hit the starter... in just a second, I could feel liquid fuel on the palm of my hand so. I put the air cleaner back on, got in and fired her up... didn't have to wait for her to cool down, just had to help the vacuum pull liquid. Now she's in the garage and I'm having an ice cold Coke...

[rheltzel]

Nice 75F day here in California. Just got back home after a 20 mile drive on the freeway. My '35 was running fine until I had to stop on the off ramp for a long signal. When the light changed, I took off and had the usual "hot engine" hiccup after shifting to 2nd and light hesitation through 2nd. Never happens when the engine is cool, only when hot. When I got home, I checked the carburetor...it was dry around the throttle shaft and base. Came back out 10 minutes later and the throttle shaft was dripping and base of carb/manifold was wet, caused, I assume, by vapor pressure in the float chamber pushing fuel down the carb.

We're still on "winter" formula gasoline here in California, which has a higher vapor pressure rating (vaporizes more readily) than summer blends, which, no doubt, is a good part of my problem. Moderns with their high-pressure fuel injection systems don't seem to care, but our old cars sure don't like it.

I've ordered an insulating base for the carb and hope that will cure or reduce the problem.

[windjammer]

An old trick was to put a "T" in the gas line after the mechanical fuel pump. In the out let of the "T" solder it closed, then drill an 1/8 hole in the solder. Run a line from the "T" to the gas filler hose.
This is what came from the factory on the old Cads.

[trainguy]

Originally Posted by windjammer

An old trick was to put a "T" in the gas line after the mechanical fuel pump. In the out let of the "T" solder it closed, then drill an 1/8 hole in the solder. Run a line from the "T" to the gas filler hose.
This is what came from the factory on the old Cads.

Explanation please,Phil

[D. Jones]

Originally Posted by windjammer

An old trick was to put a "T" in the gas line after the mechanical fuel pump. In the out let of the "T" solder it closed, then drill an 1/8 hole in the solder. Run a line from the "T" to the gas filler hose.
This is what came from the factory on the old Cads.

Sounds like it becomes a bypass pump without a check valve. When the pump is running it feeds the carburetor and the tee back to the tank until the needle valve closes then bypasses all of the fuel back to the tank. It would also provide a path for fuel to go back to the tank if vapor pressure built up. At least I think that is what would happen. Wonder how it would effect the fuel pressure to the carburetor?

[41ford1]

Originally Posted by windjammer

An old trick was to put a "T" in the gas line after the mechanical fuel pump. In the out let of the "T" solder it closed, then drill an 1/8 hole in the solder. Run a line from the "T" to the gas filler hose.
This is what came from the factory on the old Cads.

What this does is keep the fuel flowing when idling at a stop light. It is one solution to try to prevent vapor lock. Cadillac used a vacuum controlled valve on 62 models. That valve failed in a my dads car. It would vapor lock until the valve was replaced. Windjammers fix might work on the flatheads.